One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6)(7,11)(8,10)(9,12)(13,14)(15,22)(16,18)(17,21)(19,23)(20,25)(24,27)(26,28) involution — undirected(5,6)(7,11)(8,10)(9,12)(14,18)(15,23)(16,25)(19,27)(20,21)(22,26) involution — undirected(2,4)(6,10)(7,8)(11,12)(13,15,16,24,17,23,25,28)(14,19,20,27,21,22,18,26)(5,7,9,8)(6,11,12,10)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.